With the proliferation of digital audio and video devices, it has become necessary to establish a high speed serial communication mechanism that is capable of allowing efficient and fast transfer of audio/video (A/V) data between devices. IEEE 1394 has so far been a successful candidate for this purpose.
The transmission of A/V data using industry standard such as IEEE 1394 is well known. While the speedy transmission of A/V data over an IEEE 1394 bus is important, the efficient retrieval and display of A/V data by modern computing devices, such as a set top box, is also becoming an important issue. For example, when A/V data are requested from a storage medium, such as a hard disk, for display by a set top box, the time it takes to display the retrieved A/V data is critical. Regardless of how fast the A/V data can be transmitted over the IEEE 1394 bus, the retrieved A/V data do not serve their ultimate purpose if such data cannot be displayed promptly by the set top box.
Under the IEEE 1394 standard, A/V or isochronous data are organized and stored as individual packets. A number of packets are then grouped together to form a frame. When A/V data in 1394 format are displayed, the displaying device displays the A/V data one frame at a time. All the packets within a frame are collected first before a frame is displayed. As a result, in order to display a frame, the start of the frame or frame boundary need to be located. However, when a displaying device receives the retrieved A/V data from a storage medium, the beginning of such data do not necessarily, and in fact often do not, begin with a frame boundary. This is because a hard disk, for example, typically only delivers data on disk sector boundaries. As a result, the initial data delivered by the hard disk may not correspond to a frame boundary. Furthermore, data corresponding to the frame boundary may be lost due to bad or lost disk sectors or other reasons.
In addition, when partial frames are delivered to certain displaying devices, such devices may not be robust enough or have sufficient capability to handle partial frames. Consequently, such devices may not be able to display any A/V data at all. Hence, it is often necessary to locate or synchronize to the next available frame boundary before the data can be displayed. Therefore, it would be desirable to provide a method and system to efficiently synchronize the retrieved A/V data to a frame boundary so as to allow such data to be displayed more promptly.